The present invention relates generally to an apparatus for evaluating the integrity of a container seal. More particularly, the present invention relates to an apparatus for evaluating the seal integrity of liquid-filled containers of varying sizes, and the method for evaluating such seals.
Containers with resealable closures are used throughout the food and beverage industry. The closures are designed to prevent product leakage and yet they must provide the user with easy open access to the contents of the container. Resealable closures are appropriate when the container contents are beverages or food products because these closures enable consumers to dispense a desired portion of the beverage or food product and then reseal the remainder of the product for later consumption. One problem with this type of sealed container is leakage, which is more common with plastic containers.
For plastic containers, the leaks are primarily attributable to processing conditions such as heat exposure, finish abrasions, fill temperature, head space, pull-up range, and inversion. When the seal on a plastic container fails, the liquid or food contents of the container can become contaminated and the container is not suitable for sale to the public. As a result, the container and the contents must be discarded with the manufacturer experiencing a reduction in product output.
U.S. Pat. No. 5,535,618 to Konieczka and assigned to the assignee of this application, discloses a destructive method for testing for leaks in sealed containers. The method of that invention includes measuring for electrical conductivity between contents of a sealed container and an electrolyte solution in which the container is partially immersed. The method disclosed in the ""618 patent detects a container seal leak if there is electric current flowing from an electrode in a solution to a second electrode positioned within the container contents. Conversely, if no electric current flow is detected, then the container seal is not leaking.
A device currently used in accordance with the teachings of the ""618 patent for testing container seals requires the operator to perform two distinct, time consuming steps. In a first jig, the operator must pierce a surface of the container with a drill bit mounted in a drill press. Next, the operator must transport the container to a testing device and properly secure the container before beginning the testing procedure. Since the liquid contents of the container can be spilled while transporting the pierced container, the device has an inherent level of imprecision which can affect the accuracy of test results and the verification of earlier test results. In addition, the components comprising the testing devices are numerous and are not integrated into a single apparatus. As a result, the testing device is inefficiently packaged and consumes a disproportionate amount of workspace. Also, because the prior device is immobile, the operator is precluded from repositioning the testing device or temporarily moving the testing device closer to or away from the container production line. Lastly, the prior conventional test apparatus employs a manually moved member to secure and deform the container during the test process. In the conventional apparatus, developing the necessary force to deform or squeeze the container requires muscular exertion by a human operator. Accordingly, the manually moved member is subject to variation based upon the individuality of the operation and the operator, which further reduces the precision of the testing results. Also, during the course of a typical day, the operator can experience some fatigue when repeatedly applying the necessary muscular exertion to the manually moved member. Further, the manually moved member (i.e. a hand crank) requires a significant time element to operate, which further reduces the sampling rate of the device. Consequently, there is a need for an efficiently packaged, mobile device with improved precision for testing a seal on a liquid-filled container at a higher sample rate.
The present invention provides an apparatus and method for evaluating the integrity of a container seal. In general terms, the container is liquid-filled and the container wall is capable of being deformed to increase pressure within the container.
According to one aspect of the invention, the apparatus comprises a tank for containing a liquid solution. Preferably, the liquid is an electrolyte composition.
According to another aspect of the invention, the apparatus further comprises a clamp with a first and second member between which the container is engaged. The clamp is positioned with respect to the tank such that a portion of the container properly situated in the clamp will extend into the tank such that the seal will be submersed in the electrolyte solution.
According to another aspect of the invention, a ram and cylinder are operatively connected to the clamp such that the clamp can be clampingly engaged about a container by relative movement between the ram and the cylinder. The clamp is comprised of a first member and a second member. The first member is connected to one of either the ram or cylinder in a manner such that the first member is displaced toward the second member by relative movement between the ram and cylinder.
According to another aspect of the invention, a seat is provided to support a portion of the container to establish a desired position of the container with respect to the clamp before clamping occurs. The seat is located and configured such that at least a portion of the container supported by the seat will extend into the tank. This permits the container to be precisely placed in a testing position when the clamp engages and deforms the container.
According to another aspect of the invention, a drill or like means is provided to pierce a wall of the container to make an opening into the container. The drill is located such that the opening can be made while the container is positioned in the seat. Preferably, the drill is vertically adjustable along a drill support and the drill is rotatable about the support.
According to another aspect of the invention, the tank, the clamp, the seat, and the ram and cylinder are mounted on a mobile platform. Also, the support can be mounted to the tank or on the mobile platform. The mobile platform can be configured to include utility connections (e.g. compressed air, or electricity) for the drill and the ram and cylinder.
According to another aspect of the invention, the apparatus further includes a conductivity meter mounted on the platform. The meter includes a first electrode and a second electrode. After the drill makes an opening in a wall of the container, the first electrode can be inserted into the opening such that at least a portion of the first electrode is immersed in the liquid contents of the container. The second electrode can be positioned such that at least a portion of the second electrode extends into the tank.
It is contemplated that further automation can be achieved under the invention by incorporating the first probe with a means for making the opening. For example, the probe itself may be provided with a sharp tip which could be pressed, rotated, or both, to penetrate the container wall by either manual manipulation or with a press. Also, a spinning electrical contact may be associated with the drill such that the drill will act as a first electrode and a conductivity reading can be made before the drill is withdrawn from the container.
In preferred embodiments of the invention, the apparatus will be capable of evaluating the seal on liquid-filled containers of different sizes. To this end, a number of engaging surfaces may be used to facilitate the engagement of the container and the clamp. Accordingly, the engaging surfaces are adapted for the testing of different sized containers.
The present invention further relates to a method for evaluating a seal on a liquid-filled container. The container seal is determined to be leaking when the conductivity meter detects a flow of electrons from one electrode to the other electrode. Conversely, the container seal is determined as not leaking when the conductivity meter does not detect a flow of electrons from one electrode to the other electrode.